mdb on x86 should be able to print alternate register names
Currently mdb only supports the names for registers that are based on the specific targets that are in use. Thus for an amd64 target, it is only valid to register names like rax and rdx. However, it is valid to use names like eax and edx in assembly which refer explicitly to the 32-bit portions. This change adds support for all the register aliases for 32-bit and 64-bit x86 systems. This includes the 32, 16, 8 (upper and lower) byte registers.